Cold-transporting apparatus

ABSTRACT

A cold-transporting apparatus comprises a system of ducts including an outer tube having within it a first tube through which flows cold-transporting medium of a lower temperature, and a second tube through which flows cold-transporting medium of a higher temperature. Spacing elements are present between these tubes, these elements being transverse to the axial direction of the tubes and connected together via an elongate connection element of low-thermal conductivity.

United States Patent Holland 1 Oct. 2, 1973 COLD-TRANSPORTING APPARATUS 3,543,355 12/1970 Wyckoff 1311 112 x l h 2,504,478 4/1950 [75] Inventor. Jo annes Holland, Emmaslngel, 2664112 12/1953 Emdhoven, Netherlands 2,297,165 9 1952 Ringel 138/112 x [73] Assignee: U.S. Philips Corporation, New York,

Primary ,ExaminerHcrbcrt F. Ross 22 Filed; 22 971 Atl0rneyFrank R. Trifari [21] Appl. N0.: 136,410

[57] ABSTRACT [30] Foreign Application Priority Data M 25 1970 N h l d 0 560 A cold-transporting apparatus compnses a system of ay ct er an S 7 07 ducts including an outer tube having within it a first tube through which flows cold-transporting medium of [52] U.S. Cl 138/113, 138/108, 16557525, 3 lower temperature, and a second tube through which flows cold-transporting medium of a higher tempera- [51] lnt.Cl. F161 9/18 ture. Spacing elcments are pmsem between these [58] Field of Search 138/112, 113, 108; 62/55 6562 tubes, these elements being transverse to the axial d1- rection of the tubes and connected together via an Reerences Cited elongate connection element of low-thermal conductivity.

6 Claims, 9 Drawing Figures PATENTED 3,762,447 sum 1 UF 3 I NVE N TOR. JOHANNES HOLLAND BY EMMA AGENT COLD-TRANSPORTING APPARATUS The invention relates to a cold-transporting apparatus comprising a system of ducts having an outer tube in which in the axial direction thereof extend beside each other at least one first inner tube through which cold-transporting medium of a lower temperature can flow and at least one second inner tube through which cold-transporting medium of a higher temperature can flow. A number of spacing members are present between the outer tube and the inner tubes for mutually spacing the said tubes.

Apparatus of the type to which the present invention relates are known from French Pat. No. 1,552,391 and U.S. Pat. specification No. 3,473,341. In these apparatus it is usual to use as spacing members, plates which are arranged transverse to the axial direction and which are connected mechanically, and hence also thermally, both to the first and to the second inner tube.

A drawback of this construction is that during operation of the device a comparatively large amount of thermal energy flows from the second inner tube which is at a higher temperature to the first inner tube which is at a lower temperature, due to conduction via the spacing members in the form of plates, which involves an undesirable reduction of the cold capacity of the transporting medium in the first inner tube. In order to slightly restrict the flow of thermal energy, the plates are preferably manufactured from a material which poorly conducts heat.

It is the object of the present invention to provide a cold apparatus in which the transport of thermal energy from the second to the first inner tube is considerably reduced. The invention is based on the recognition of the fact that a reduction of the flow of thermal energy can be obtained by considerably increasing the distance which the thermal energy has to cover to come from the second to the first inner tube, and thereby considerably increasing the thermal resistance.

In order to realize the end in view the apparatus according to the invention is characterized in that each spacing member is constituted by an assembly of at least one first and at least one second supporting element, which elements extend mainly transverse to the axial direction and, viewed in the axial direction, are mutually spaced, said supporting elements being connected together via an elongate connection element which poorly conducts thermal energy and extends mainly in the axial direction, each of the supporting elements having such a shape, that the first supporting element contacts only the first of the two inner tubes and holds said first tube in its place relative to the outer tube, the second supporting element contacting only the second of the two inner tubes and holding said second inner tube in its place relative to the outer tube. In this manner it is achieved that thermal energy can flow from the second to the first inner tube only via the elongate connection element and the two supporting elements. Since the connection element has a low coefficient of thermal conductivity and, in the direction of flow of the thermal energy, a large length with a small cross-section, the thermal resistance of said element is high and only a very small heat transport from the second to the first inner tube takes place.

In a favorable embodiment of the device according to the invention the supporting elements are constituted by flat plates each comprising a bore in which the relevant inner tube can be held in its place and comprising a recess for the freely passing inner tube, said plates being connected together via a hollow pipe. This presents the advantage that a simple construction which can readily be assembled is obtained with a minimum of material and a maximum of thermal resistance as well as a large mechanical strength due to the large rigidity of pipes as compared with rods and the like.

A further favorable embodiment of the device accordng to the invention is characterized in that the supporting elements and the connection elements are manufactured from the same poorly heat-conducting material. Only one starting material for both the supporting elements and the connection elements is of course advantageous. Moreover, it is possible in a number of 5 cases to compose the spacing members not from the components of the same material but to manufacture them in one operation as one assembly.

In a further favorable embodiment of the device according to the invention the material is stainless steel. Stainless steel is comparatively cheap, has a low coefficient of thermal conductivity, can be realized in the form of pipes in all kinds of diameters and wall thicknesses, and can be readily machined. Connection of stainless steel spacing members to the inner tubes can be carried out by soldering or welding.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawings which are diagrammatic and not drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. la is a fragmentary elevation view of a system of ducts of this invention.

FIG. lb is a cross-sectional view taken along line Il of FIG. Ia.

FIG. 1c is an elevation view of a spacing member of FIG. la.

FIG. 1d is an end view of FIG. lc.

FIG. 2a is an elevation view in section of a cold gas refrigerator combined with a cold transport apparatus of this invention.

FIG. 2b is a front elevation view enlarged of a portion of FIG. 2a.

FIG. is an end view of FIG. 2b, taken along line IIII of FIG. 2b.

FIG. 2d is an elevation view of a spacing member of FIG. 2b.

FIG. 2e is an end view of FIG. 2d taken along line III- III of FIG. 2d.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1a denotes a system of ducts of a cold-transporting apparatus (not shown), which system comprises an outer tube 2, within which a first inner tube 3 and a second inner tube 4 extend beside each other in the axial direction. Between the tubes is a spacing member 5 which consists of a first supporting plate 6 and a second supporting plate 7 which are rigidly secured together by means of a pipe 8 of a poorly heat conducting material, for example, stainless steel. In this case the plates 6 and 7 are identical, each have a bore 9 and 9Lrespectively and 10. respectively and a recess 10, and are arranged around the axis of the pipe 8 while rotated 180 relative to each other.

The first inner tube 3 is spaced apart relative to the outer tube 2 in the bore 9 of the first supporting plate 6, and via recess of the second supporting plate 7, it extends along said plate without contacting it.

The second inner tube 4 is spaced from the outer tube 2 in the bore 9' of the second supporting plate 7 and, via the recess 10 of the first supporting plate 6, it extends along said plate without contacting it. Plate 6 contacts outer tube 2 via narrow legs 6a, 6b and plate 7 contacts outer tube 2 via narrow legs 7a and 7b.

During operation of the cold-transporting apparatus, transport of cold at lower temperature takes place through the first inner tube 3 by means of a coldtransporting medium flowing through said tube. Transport of cold at higher temperature takes place simultaneously through the second inner tube 4, likewise by a cold transporting medium flowing through this tube. The first inner tube 3 then has a lower temperature than the second inner tube 4. Heat transfer by conductivity from the warmer inner tube 4 to the colder inner tube 3 can take place only via successively the supporting plate 7, the pipe 8 and the supporting plate 6. As a result of the long conductivity path of the pipe 8 of poorly heat conducting material and of comparatively small cross-section, heat transport by conductivity is substantially entirely prevented.

FIG. 2a shows a cold-transporting apparatus which is incorporated between a cold-gas refrigerator and an object to be cooled. Reference numeral 11 denotes a two-stage cold-gas refrigerator which comprises a piston l2 and a displacer 13 which consists of two parts 131 and 13" of different diameters. The piston 12 and the displacer 13 are connected to a driving mechanism (not shown) by a piston rod 14 and a displacer rod 15, respectively, the driving mechanism being capable of moving the piston and the displacer with a mutual phase difference. Above the piston 12 is a compression space 16 which communicates with an intermediate expansion space 20 via a cooler 17, a first regenerator 18, and a first freezer 19. The intermediate expansion space 20 communicates via a second regenerator 21 and a second freezer 22 with a final expansion space 23. In the intermediate expansion space 20 this coldgas refrigerator supplies cold at a temperature of approximately 70 K, while in the final expansion space 23 cold is supplied at a temperature of approximately 20 K. The device comprises a system of ducts 24 which at one end is in a heat exchanging relationship with the second freezer 22 at 25, and at the other end can exchange heat with an object (not shown) at 26. The system of ducts 24 comprises a cold-transporting medium which is circulated by a pump 27.

Around those parts of the apparatus which during operation assume a low temperature a wall 28 is provided and the space within the wall 28 can be evacuated. In order to restrict thermal radiation from the wall of the vacuum space to the parts which are at the lower temperature, said walls are screened from the wall 28 by radiation screens 29 and 30 which are shown diagrammatically. The radiation screen 30 has a tubular construction and is in a heat-conducting contact with a further system of ducts 31 which also comprises a coldtransporting medium which is also circulated by the pump 27 and which cools the radiation screen 30. The further system of ducts 31 is for that purpose in a heat exchanging relationship with the first freezer 19 at 32.

Spacing members 33 are secured between the tubular radiation screen 30, the system of ducts 24 which is at a lower temperature during operation, and the system of ducts 31 which is at a higher temperature during op eration. For clarity this is not shown in FIG. 2a but for one spacing member separately this is shown in the front elevation of FIG. 2b and in the side elevation of FIG. 2c.

Spacing member 33 consists of a pipe 34 to which in the center a first supporting element 35 and at the ends second supporting elements 36 are secured. The first supporting element 35 is of such a shape that the two parts of the duct of the further system of ducts 31 which is at a higher temperature are guided past it and comprises two bores 37 in which the two parts of the duct of the system of ducts 24 which is at a lower temperature are held in their places.

The second supporting element 36 is of such a shape that the two parts of the duct of the system of ducts 24 which is at a lower temperature are guided past it. The second supporting element 36 furthermore comprises a bore 38, in which one part of the duct of the further system of ducts which is at the higher temperature is spaced from the radiation screen 30 and comprises a recess 39 in which the other part of the duct of the further system of ducts is incorporated. This latter part of the duct is also secured to the radiation screen 30 to cool said screen. For reasons of assembling, the recess 39 is present instead of a bore. The diameter of the first supporting element 35 is smaller than that of second supporting elements 36, as a result of which only the two second supporting elements 36 are in direct contact with the radiation screen 30.

During operation of the device only a very small amount of thermal energy can flow by conductivity from the further system of ducts 31 which is at a higher temperature to the system of ducts 24 which is at a lower temperature via successively the second supporting elements 36, pipe 34, and first supporting element 35, which is extremely favorable for a good efficiency of the cold transport at the lower temperature.

I claim:

1. Cold transport apparatus comprising an outer tube having a bore defined by inner walls thereof, a first inner tube axially positioned within said bore and transversely spaced from the walls thereof, second inner tube axially positioned within said bore and spaced transversely from the walls thereof and from the first inner tube, at least one spacing member means comprising first and second support elements, axially spaced apart and each extending generally transverse of said tubes axes, the first support element engaging only and maintaining separate the first inner tube and said bore walls, the second support element engaging only and maintaining separate the second inner tube and said bore walls, and a connection element having low thermal conductivity and extending axially between and engaging said first and second support elements, whereby the first and second inner tubes are in contact only via a path including both support elements and the connecting element therebetween.

2. Apparatus according to claim 1 wherein each of said supporting elements comprises a generally flat plate having a bore through which extends and in which is engaged one of said inner tubes, and a recess through with the other of said inner tubes passes axially.

6 3. Apparatus according to claim 1 wherein siad conporting elements have low thermal conductivity. nectmg element a tube 6. Apparatus according to claim 5 wherein said low 4. Apparatus according to claim 2 wherein said connecting element is a tube.

5. Apparatus according to claim 1 wherein said sup- 5 conductivity elements are stainless steel. 

1. Cold transport apparatus comprising an outer tube having a bore defined by inner walls thereof, a first inner tube axially positioned within said bore and transversely spaced from the walls thereof, second inner tube axially positioned within said bore and spaced transversely from the walls thereof and from the first inner tube, at least one spacing member means comprising first and second support elements, axially spaced apart and each extending generally transverse of said tubes'' axes, the first support element engaging only and maintaining separate the first inner tube and said bore walls, the second support element engaging only and maintaining separate the second inner tube and said bore walls, and a connection element having low thermal conductivity and extending axially between and engaging said first and second support elements, whereby the first and second inner tubes are in contact only via a path including both support elements and the connecting element therebetween.
 2. Apparatus according to claim 1 wherein each of said supporting elements comprises a generally flat plate having a bore through which extends and in which is engaged one of said inner tubes, and a recess through which the other of said inner tubes passes axially.
 3. Apparatus according to claim 1 wherein siad connecting element is a tube.
 4. Apparatus according to claim 2 wherein said connecting element is a tube.
 5. Apparatus according to claim 1 wherein said supporting elements have low thermal conductivity.
 6. Apparatus according to claim 5 wherein said low conductivity elements are stainless steel. 